• The Korean Journal of Applied Statistics
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• v.26 no.1
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• pp.151-162
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• 2013

Due to a growing demand for the second-hand product, especially for the expensive one, the warranty and maintenance policies for such products have been studied to improve the product reliability of late. In this paper we study a periodic maintenance model for the second-hand product which is purchased by the customer at the age of $x$. When purchased, the dealer provides a warranty of a fixed length during which the product is maintained periodically to reduce the failure rate of the product and thus, to improve the reliability after each maintenance is served. If a failure occurs between two successive maintenances, only minimal repair is conducted. As for the warranty policy, we adopt free non-renewing repair action on each failure, in addition to the periodic maintenance service during the warranty period. Thus, under the given warranty policy, all the maintenance and repair costs incurred during the warranty period are charged to the dealer. For the proposed periodic maintenance scheme, we formulate a cost model to evaluate the expected total cost charged to the dealer during the warranty period and derive an optimal upgrade level of the failure rate at each maintenance to minimize the expected total warranty cost from the perspective of the dealer. We also present numerical results for an optimal upgrade level based on the proposed methods.

• The Journal of Society for e-Business Studies
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• v.24 no.3
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• pp.19-33
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• 2019

Recently, manufacturers have been struggling to efficiently use production equipment as their production methods become more sophisticated and complex. Typical factors hindering the efficiency of the manufacturing process include setup cost due to job change. Especially, in the process of using expensive production equipment such as semiconductor / LCD process, efficient use of equipment is very important. Balancing the tradeoff between meeting the deadline and minimizing setup cost incurred by changes of work type is crucial planning task. In this study, we developed a scheduling model to achieve the goal of minimizing the duedate and setup costs by using reinforcement learning in parallel machines with duedate and work preparation costs. The proposed model is a Deep Q-Network (DQN) scheduling model and is a reinforcement learning-based model. To validate the effectiveness of our proposed model, we compared it against the heuristic model and DNN(deep neural network) based model. It was confirmed that our proposed DQN method causes less due date violation and setup costs than the benchmark methods.

• Korean Journal of Construction Engineering and Management
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• v.22 no.3
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• pp.79-90
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• 2021

In domestic public construction, disputes are increasing due to differences among stakeholders regarding contract price adjustment. In particular, the actual cost-plus fee for overhead costs due to the schedule extension cannot be agreed upon at the administrative phase, and most of them seek judicial judgment. Thus, this study aims to propose a 'sufficiently satisfactory' alternative to reach an agreement before disputes in order to minimize disputes related to the calculation of additional overhead costs. To this end, this study proposes three alternatives based on the rate method. Firstly, when calculating additional overhead costs, it is not calculated as an actual cost-plus-fee method, but as a rate compared to direct labor costs among net direct costs. Secondly, the calculated indirect labor costs are compensated for up to the legal maximum of legal limit costs such as general management costs, profits and so on. Thirdly, it reflects overhead costs increased or decreased due to change orders. Risks were analyzed by collecting expert opinions on the proposed methods and applying actual cases. Finally, as a result of investigating the level of consensus for each stakeholder, it was confirmed that all stakeholders could agree regardless of the size of the company. The result of this study is expected to as a useful tool among stakeholders in the construction fields that can be able to easily agreed upon.

• Environmental and Resource Economics Review
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• v.32 no.2
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• pp.127-147
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• 2023

This study is trying to analyze the economic effect of replacing thermal power generation, one of the government's carbon-neutral policies, with new and renewable energy. For this analysis, scenario A is set to replace 100% of thermal power generation with new and renewable energy, and scenario B is set to replace 60% of thermal power generation with new and renewable energy. In addition, costs are incurred when replacing thermal power generation with new and renewable energy, and scenario 1 is the same cost as the current cost, and scenario 2 is120% higher than the current cost. Therefore, when converting thermal power generation to new and renewable energy, the scenarios are largely organized into four cases. In the case of replacing thermal power generation with new and renewable energy, the production inducement coefficient of thermal power generation decreased from the current level regardless of the scenario. However, the value-added inducement coefficient and the greenhouse gas emission inducement coefficient are lower than the current level when thermal power is converted to renewable energy by 100%, while the value-added inducement coefficient and greenhouse gas emission inducement coefficient are higher than the current level. In addition, the greenhouse gas emission induction coefficient of most industries was found to decrease, while the production induction coefficient and the value-added induction coefficient increased. Scenario A seems appropriate because the purpose of the government's policy is to reduce greenhouse gas emissions by converting thermal power into new and renewable energy. However, as a result of this, the production inducement coefficient and value-added inducement coefficient of some industries decrease, so the government's support policy is needed to solve this problem

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1160-1168
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• 2000

This paper presents a real-time integrated traffic management (RITM) scheme that can effectively manage variable bit rate (VBR) and available bit rate (ABR) traffics having unpredictable characteristics in asynchronous transfer mode (ATM) networks. An unique feature of this scheme is that it has a special ATM cell control block which makes it possible to monitor bursty traffics in real-time so that the delay incurred to measure cell arrival rate is minimized. Additionally, the proposed scheme intends to dynamically reassign the leftover network resources to VBR/ABR connections without any deterioration in quality of service (QoS) of the existing connections. The RITM scheme has been verified to reliably monitor incoming traffics and to efficiently manage network resources by computer simulations. The capability of managing the incoming ATM traffics in real-time helps determine an optimal acceptable number of user connections for a given network condition. We can use this value as a threshold to protect the network from being congested and to find out a cost-effective buffer design method.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.4
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• pp.609-624
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• 2003

The genesis of methods for defining the nutritional value of feeds and the nutrient requirements of animals, and their development in the late 19th and early 20th centuries in Europe and the USA are outlined. Current energy and protein feeding systems for ruminants are described. Particular reference is made to the Australian systems which are applicable to grazing animals as well as to those given prepared feeds, and enable the effective nutritional management of a imals at pasture by means of the decision support tool GrazFeed. The scheme for predicting intakes by cattle and sheep from pastures allows for the effects of selective grazing on the composition of the feed eaten, and for reduction in herbage intake when a supplementary feed is consumed. For herbage of any given concentration of metabolizable energy (ME) in the feed dry matter the changes with season of year in the net efficiency of use of the ME for growth and fattening and in the yield of microbial crude protein, g/MJ ME, which both vary with latitude, are defined. An equation to predict the energy requirements for maintenance (MEm) of both cattle and sheep includes predictions of the additional energy costs incurred by grazing compared with housed animals and the cost, if any, of cold stress. The equation allows for the change in MEm with feed intake. A flexible procedure predicts the composition of liveweight gain made by any given breed or sex of cattle and sheep at any stage of growth, and the variation with rate of gain. Protein requirements for maintenance, production including wool growth, and reproduction, are related to the quantities of microbial true protein and undegraded dietary protein truly digested in the small intestine.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.4
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• pp.90-96
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• 2016

Incremental sheet forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. Compared to conventional sheet forming processes, ISF is of a clear advantage in manufacturing small batch or customized parts. ISF needs die-less machine alone, while conventional sheet forming requires highly expensive facilities like dies, molds, and presses. This equipment takes long time to get preparation for manufacturing. However, ISF does not need the full facilities nor much cost and time. Because of the facts, ISF is continuously being used for small batch or prototyping manufacturing in current industries. However, spring-back induced in the process of incremental forming becomes a critical drawback on precision manufacturing. Since sheet metal, being a raw material for ISF, has property to resilience, spring-back would come in the case. It is the research objective to investigate how geometrical shaping parameters make effect on shape dimensional errors. In order to analyze the spring-back occurred in the process, this study experimented on Al 1015 material in the ISF. The statistical tool employed experimental design with factors. The table of orthogonal arrays of $L_8(2^7)$ are used to design the experiments and ANOVA method are employed to statistically analyze the collected data. The results of the analysis from this study shows that the type of shape and the slope of bottom are the significant, whereas the shape size, the shape height, and the side angle are not significant factors on dimensional errors. More error incurred on the pyramid than on the circular type in the experiments. The sloped bottom showed higher errors than the flat one.

• Korean Journal of Construction Engineering and Management
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• v.5 no.6 s.22
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• pp.110-117
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• 2004

The environmental-related disputes and claims are steeply increasing recently. Among them the number of disputes and claims on noise and vibration incurred in the process of construction is more than $85\%$. Since those disputes and claims cause cost overrun and or penalty and bad impression for the construction company, it is necessary to develop a systematic management method for solving them. This study presents a environmental management structure based on the examining many kinds of environmental-related laws including 'The Act on Regulation of Noise and Vibration' furthermore, through analysing various dispute and claim cases, and surveying literatures we suggest environmental study noise and vibration management method using for the preconstruction phase, the construction phase and the post construction phase, respectively.

• Journal of Internet Computing and Services
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• v.17 no.1
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• pp.7-14
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• 2016

Recently, as cloud computing technologies are developed, it enable to work anytime and anywhere by smart phone and computer. Also, cloud computing technologies are suited to reduce costs of maintaining IT infrastructure and initial investment, so cloud computing has been developed. As demand about cloud computing has risen sharply, problems of power consumption are occurred to maintain the environment of data center. To solve the problem, first of all, power consumption has been measured. Although using power meter to measure power consumption obtain accurate power consumption, extra cost is incurred. Thus, we propose prediction method about power consumption without power meter. To proving accuracy about proposed method, we perform CPU and Hard disk test on cloud computing environment. During the tests, we obtain both predictive value by proposed method and actual value by power meter, and we calculate error rate. As a result, error rate of predictive value and actual value shows about 4.22% in CPU test and about 8.51% in Hard disk test.

• The KIPS Transactions:PartD
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• v.13D no.1 s.104
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• pp.11-22
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• 2006

As we are to deal with more and more XML documents, research on storing and managing XML documents in databases are actively conducted. Employing RDBMS or ORDBMS as a repository of XML documents is currently regarded as most practical. The query results out of XML documents stored in databases could be cached for query performance though the cost of cache consistency against the update of the underlying data is incurred. In this paper, we assume that an ORDBMS is used as a repository for the XML query cache as well as its underlying XML documents, and that XML query cache is refreshed in a deferred way with the update log. When the same XML document was updated multiple times, the deferred refresh of the XML query cache may Bet inefficient. We propose an algorithm that removes or filters such duplicate updates. Based on that, the optimal SQL statements that are to be executed for XML query cache consistency are generated. Through experiments, we show the efficiency of our proposed deferred refresh of XML query cache.